The “/dev/null” trick does have performance issues, and depending on what version of fortran and what compiler you are using opening more than one file to “/dev/null” can be unsupported … there have been long discussions about that, some of which are still in the fortran newsgroup. There are lots of reasons I would discourage that myself, but I have seen that heavily used to avoid writing many “if(debug)write(…)…” statements. It would be nice if there were a way to literally turn off a LUN, or even some option on the write; and there are a few tricky codes that call functions with side effects in WRITE statements that would be particularly problematic. I personally wish a LUN could be an array, including being an empty array; which would allow “turning off” a WRITE and also allow writing to multiple files like the screen and a log file efficiently.